230 Abstracts FIRDAs était retrouvées pour tous les patients séropositifs, le plus souvent de fac ¸on transitoire. Seulement une patiente a présenté au cours de son suivi des LPDs dans près d’1/3 des tracés. Une amé- lioration nette des EEG après immunothérapie était notée pour la quasi-totalité de patients. Conclusion La présence d’une activité lente thêta/delta focale était commune pour l’ensemble des patients mais aspécifique. Les patients séropositifs ont tous présenté sur au moins un tracé des FIRDAs, non retrouvées pour le patient séronégatif. L’amélioration des tracés après immunothérapie révèle l’importance de recher- cher cette étiologie. Aucun pattern commun n’a été retrouvé en dehors d’une activité lente thêta/delta focale. La présence de FIRDA n’était retrouvée que chez les patients séropositifs. Mots clés EEG ; Encéphalite dysimmunitaire ; FIRDA Déclaration de liens d’intérêts Les auteurs déclarent ne pas avoir de liens d’intérêts. https://doi.org/10.1016/j.neucli.2018.06.026 26 HR-EEG Source localization Martine Gavaret Service de neurophysiologie clinique, centre hospitalier Sainte-Anne, 1, rue Cabanis, 75014 Paris, France E-mail address: martine.gavaret@parisdescartes.fr High-resolution EEG (HR-EEG) allows the recording of electric brain activities with excellent temporal resolution. Data have to be recor- ded with high temporal resolution (sampling rate) and high spatial resolution (number of channels). Data analyses are based on several steps including interictal and/or ictal selections, head model ela- boration and use of several algorithms in order to solve the inverse problem. These tools now represent real methods of Electric Source Imaging. HR-EEG constitutes non-invasive and complementary exa- mination with Magnetoencephalography (MEG), characterized by distinct sensitivities according to the location and orientation of intracerebral generators. In the presurgical assessment of drug- resistant partial epilepsies, HR-EEG can characterize and localize interictal activities and thus the irritative zone. HR-EEG often yields significant additional data that are complementary to other presur- gical investigations. In some lesional epilepsy cases as epilepsies related to focal cortical dysplasia, localization of the irritative zone using HR-EEG is particularly relevant in presurgical evalua- tion, epileptogenic and irritative zones being characterized by an overlap. It has been demonstrated that HR-EEG more accurately estimated the epileptogenic zone in subgroups of patients who are often the most difficult cases in epilepsy surgery: frontal lobe epilepsy, negative MRI and the presence of malformation of cor- tical development [1]. Moreover, source localization results may help in identifying subtle focal cortical dysplasia abnormalities and increasing the diagnostic yield of conventional MRI visual analysis [3]. During presurgical evaluation of pharmacoresistant partial epi- lepsies, stereoelectroencephalography records interictal and ictal activities directly but is inherently limited in spatial sampling. In contrast, scalp-EEG and MEG are less sensitive but provide a global view on brain activity. Therefore, recording simultaneously these three modalities [2] should provide a better understanding of the underlying brain sources by taking advantage of the different sen- sitivities of the three recording techniques. Keywords Epilepsy; Interictal spikes; Pre-surgical investigation Disclosure of interest The author declares that he has no com- peting interest. References [1] Abdallah C, Maillard LG, Rikir E, Jonas J, Thiriaux A, Gavaret M, et al. Localizing value of electrical source imaging: Fron- tal lobe, malformations of cortical development and negative MRI related epilepsies are the best candidates. Neuroimage Clin 2017;16:319—29. [2] Dubarry AS, Badier JM, Trébuchon-Da Fonseca A, Gavaret M, Car- ron R, Bartolomei F, et al. Simultaneous recording of MEG. EEG and intracerebral EEG during visual stimulation: from feasibility to single-trial analysis. Neuroimage 2014;99:548—58. [3] Wang ZI, Alexopoulos AV, Jones SE, Najm IM, Ristic A, Wong C, et al. Linking MRI postprocessing with magnetic source imaging in MRI-negative epilepsy. Ann Neurol 2014;75:759—70. https://doi.org/10.1016/j.neucli.2018.06.027 27 Altération de la perception visuelle élémentaire en psychiatrie Anne Giersch Inserm U1114, pôle de psychiatrie, CHRU de Strasbourg, Strasbourg, France Adresse e-mail : giersch@unistra.fr Objectives Abnormalities in visual perception are not at the foreground of schizophrenia symptomatology [1—3]. They are none- theless often found in the patients’ complaints during prodromal phases, and have been described as one of the best predictor of schi- zophrenia conversion. What is the link between perceptual disorders and clinical symptoms in schizophrenia ? After a short discussion of different perceptual abnormalities, we will focus on the time struc- ture of perception, that illustrates possible links between low-level perception disorders, predictive coding and the sense of minimal self (the self that helps to feel as being present here and now). Methods We tested the link between the sense of self and time disorders in 28 stabilized patients with schizophrenia and 24 mat- ched controls. We evaluated time expectation, as indexed by the ability to benefit from the passage of time to react to a visual tar- get : expectation increases with time, leading to shorter reaction times. We additionally check to which amount this phenomena is modulated when the targets are missing in some trials, and can be compensated for by attention cues. In parallel, minimal self- disorders were evaluated with the EASE (phenomenological scale). Results Patients can expect sensory signals and react to unu- sual events like missing targets as well as controls. However, the patients who display disorders of the minimal self (EASE) do not benefit from the passage of time, and all patients display disrupted time expectation when the occurrence of events is uncertain. Conclusion The results suggest a link between timing and minimal self disorders. Time expectation helps to link events with one ano- ther and to transform a chain of discontinuous events in a continuous flow. Conversely, fragile time expectations may lead to a sense of discontinuity, which could disrupt the flow of sensory signals, thus contributing to minimal self-disorders. Mots clés Perception ; Schizophrénie ; Temps Déclaration de liens d’intérêts L’auteur déclare ne pas avoir de liens d’intérêts. Références [1] Giersch A, Lalanne L, Isope P. Implicit Timing as the Missing Link between Neurobiological and Self-Disorders in Schizophrenia? Front Hum Neurosci 2016;10:303. [2] Martin B, Franck N, Cermolacce M, Falco A, Benair A, Etienne E, et al. Fragile temporal prediction in patients with schizophrenia is related to minimal self-disorders. Sci Rep 2017;7:8278. [3] Silverstein SM, Keane BP. Perceptual organization impairment in schizophrenia and associated brain mechanisms: review of research from 2005 to 2010. Schizophr Bull 2011;37:690—9. https://doi.org/10.1016/j.neucli.2018.06.028